1. Field of the Invention
The present invention relates to a method, system, and program for managing a multi-page document.
2. Description of the Related Art
In publishing, the pages of a document are scanned, transformed into a printer readable format, and then printed and/or archived in a computer storage device for subsequent retrieval and printing. Publishing software is used by publishing companies to electronically print and archive books. Pages of a document are scanned to produce an electronic bit-map representation of the pixels on the scanned page and the pixel color values. The page may contain line art, e.g., text and lines, and/or continuous tone, e.g., images. For black and white images, the scanned image is stored as a grey scale image wherein each pixel represented on the bit map has a corresponding shade of grey value. Optical scanners typically allow for anywhere from 16 to 256 shades of grey for each pixel. A bit map of a page that allows for grey scale values requires 4 to 8 bits for each pixel to indicate the different shades of grey. A bit map representing text only, where the pixel is either black, i.e., “on” or white, i.e., “off,” only requires 1 bit per pixel to indicate either “on” or “off,” black or white. A bit map that represents a color page, including line art and continuous tone, requires even more space than black and white images. Each pixel of a scanned color image can be one of 16.7 million colors, which requires 24 bits for each pixel.
After the page is scanned, the bit map produced by the scanner must be further processed into a bit map format that the printer can process. The transformation of the scanned bit map into a printer readable format is referred to as halftoning or raster image processing (RIP). In a publishing environment, halftoning or transforming, i.e., RIPping, numerous bit maps that represent the pages of a large document, such as a book, can take several hours. The result of the halftone transformation is a bi-level image, where each bit map value indicates either black or white. The halftoning transformation would use screening and dithering algorithms to produce a wide level of shades of grey or colors. Dithering refers to the illusion of printing colors or shades of grey by varying the patterns of dots. Thus, a bit map where each bit map value can correspond to one of many values indicating different shades of grey or colors is converted to a bi-level bit map where each value indicates one of two colors—black or white. However, the halftoning or transformation process uses dithering to simulate the shades of grey or different colors. The term “gray scale” as used herein refers to a bit map where each bit map value can be one of numerous values, indicating different colors or shades of grey. The term “halftone” as used herein will refer to the transformed grey scale bit map to a bit map that can be processed by the printer.
A halftone bitmap may be a bi-level bit map where there is only one value for each pixel, i.e., 0 or 1. Additionally, contone printers print a limited number of shades of a color or grey. Thus, a halftone bit map for a contone printer may include a limited number of values for each bit map value and also use dithering to simulate additional shades of grey and color. The term “halftoning” as used herein refers to the transform process of transforming a gray scale bit map to a printer readable format, such as a bi-level bit map or contone bit map capable of a limited number of different values for each pixel that are available on the printer. Halftone bit maps are typically specific to a particular printer, i.e., device dependent.
The gray scale or halftoned bit map of each page in the book may be stored in one or more files. For instance, the tagged image file format (TIFF)** stores one bit map for each page in a single file. A TIFF file can store both the gray scale bit map and a halftoned bitmap. **TIFF and PostScript are trademarks of Adobe Systems Inc.; IBM, AIX, OS/2, and RS/6000 are registered trademarks of IBM and OS/390, INFOPRINT, and MVS are trademarks of IBM; WINDOWS is a registered trademark of Microsoft Corporation; UNIX is a registered trademark licensed by the X/Open Company LTD. 
The gray scale bit map is referred to as device independent because it represents the image without reference to a specific device. The halftone bit map is device dependent as the gray scale bit map was transformed, e.g., screened or halftoned, into a halftone bit map that is particularly suited to the dithering capabilities of the printer on which the halftone bit map will be printed.
In publishing environments, to reprint copies of a book, a person will manually scan each page of a book. If there are images on a page, then the person must use a software tool to manually select the image section with the software tool and then screen the image section to produce a halftone bitmap of the image. This process of digitizing a document or book to publish is very tedious, time consuming and requires substantial labor costs.
Moreover, once the halftone is produced for one specific output device, such as a particular printer having specific characteristics, outputting that halftoned image on other printer types may produce unpredictable and undesirable output, such as moire effects. To provide optimal image reproduction, the publisher would have to rescreen the image on the page to produce a new halftone for other printers on which the document will be reproduced.
For all the above reasons, there is a need in the art to provide an improved technique for scanning and publishing books or documents in a digital printing environment.